The current behavior for a failed request is just to log it in the
output panel. When applyTweak fails for whatever reason, users usually don't get
informed (unless they open the output panel and dig the log).
this patch is to surface these errors by prompting up a message diag.
Is this how default implementation behaves? Is there a way to call into it instead of re-implementing?
If so, it would be nice to do so. If not, I'm also ok if we keep it.